New pest found in Ohio soybean fields

A new pest has been identified in Ohio soybeans, but whether or not its presence will be a problem remains to be seen.

Ohio State University Extension entomologist Ron Hammond says the root mealybug has been found in some soybean fields. The insect was first identified in Kentucky last year and has been found across the Midwest this year.

The mealybug is a tiny insect found on a number of plant species including soybeans. The particular insect being found in Midwest states such as Ohio and Iowa is known as a trochanter mealybug (Pseudococcus sorghiellus). The trochanter mealybug is a root feeder, much like the soybean cyst nematode, and exhibits sap-sucking traits, like the soybean aphid, said Hammond.

"We haven't spent a lot of time looking at root pests, because we don't have a lot of them that impact our soybean crop, so things right now are a bit up in the air in terms of their distribution and if it's something we need to be concerned about," Hammond says in a university report.

Hammond said that the trochanter mealybug was discovered when OSU Extension specialists found egg masses on the roots of soybean plants exhibiting the classic yellowing appearance from what they thought to be a potassium deficiency. But when soil tests were conducted, no potassium deficiencies were found. Similar experiences were being reported in other states where the trochanter mealybug has been found.

"It is not known if there is a cause and effect relationship (does the mealybug feeding on the roots cause the symptoms) or even if there is a relationship between those symptoms, the potassium deficiency, and the mealybugs. We often see similar symptoms on soybeans with the presence of heavy soybean aphid feeding," Hammond says. "Also, so far most of the fields where the mealybug is showing up have a history of other legumes in the rotation, so is that playing a role. This is a brand new thing and it could turn out to be nothing or it could turn out to be something we need to be concerned with. Everything so far points to the fact that we need to pay closer attention to this."

Growers experiencing potassium-like deficiencies in their soybean crop are being asked to dig up some of the plants and examine the roots to see if any mealybugs are present. A hand lens will be necessary to adequately identify the insect, but it should at least be noticeable to the naked eye because of a waxy coating, which gives it a whitish appearance.

A new pest has been identified in Ohio soybeans, but whether or not its presence will be a problem remains to be seen.